Active: Vladimir sinks into a pool of blood becoming untargetable for 2 seconds and slowing enemies above him by 40% for 1 second. Additionally, he deals magic damage every half second to them and heals himself for 12.5% of the damage done.
Cost: 20% of current health
Radius of AoE: 150
Cooldown: 26/23/20/17/14 seconds
Magic Damage Per Half-Second: 20/33.75/47.5/61.25/75 (+3.75% of bonus health)
Maximum Magic Damage: 80/135/190/245/300 (+15% of bonus health)

Active: Vladimir infects all enemies in the target area with a virulent plague which increases the damage they take from all sources by 12% for 5 seconds. After these 5 seconds, infected enemies take magic damage.
No cost:
Range to center of AoE: 700
Radius of AoE: 175
Cooldown: 150/135/120 seconds
Magic Damage: 150/250/350 (+0.7 per ability power)

+400 Health
+100 Ability Power
UNIQUE Passive: Damaging spells and abilities apply a Movement Speed reduction to enemies based on the spell type:
Single Target: 40% reduction for 1.5 seconds.
Area of Effect: 40% reduction for 1 seconds.
Damage over Time or Multi-hit: 20% reduction for 1 seconds.
Summoned Minions: 20% reduction for 1 seconds.
(If a spell fits in more than one category, it uses the weakest slow value.)

Zhonya's Hourglass

+100 Ability Power
+45 Armor
UNIQUE Active - Stasis: Champion becomes invulnerable and untargetable for 2.5 seconds, but is unable to move, attack, cast spells, or use items during this time (90 second cooldown).

Endgame items

Enchantment: Alacrity

Limited to 1 of each enchantment type.
Enchants boots to have Alacrity bonus.
UNIQUE Passive - Alacrity: +20 Movement Speed
(Unique Passives with the same name don't stack.)

Why these items?

You start up with boots and 4 pots to have a a lot of sustain and also be able to poke at your enemies as often as you can (you should save your Q for that, use for farming only when necessary). Next, You go back and start building Spirit of the Spectral Wraith, starting with a Hextech Revolver (the Spell Vamp helps you A LOT).
The Cooldown Reduction from the Ionian Boots of Lucidity helps you a lot, lets you spam your Q and E a lot.
I choose Rylai's since it has everything you need: Health and AP (health is really good to become tankyer, and you also gain some AP from it, from you passive) , and also applies a slow effect to enemies, which helps you kite them a lot.
Zhonya's is also really good on Vladimir, since it helps him be even more annoying. You can run from pretty much everyone if you kite them well and you have Zhonya's.
Liandry's Torment is also really good for the same reason that Rylai's is good: Health and AP. Also, the unique passives are really good.
Only buy Warmog's or Void Staff if you think it's necessary: if the enemy team has a lot of burst buy Warmog's. If they have a lot of MR, buy Void Staff.

Skillorder

Why this Skillorder?

Well, it's the best there is in my opinion: Q is Vladimir's main damage source, you put one point into your W, which is your escape (you can max this after Q if you have a lot of problems on your lane and have to play deffensively). Tides is also really good, since it helps you heal a lot more with your Q, if all 4 stacks are up (try to keep those stacks up, but be careful not to push your lane too much).
Hemoplague, your ultimate, is really good for teamfights and turret diving (if you want to tower dive use Ghost first, than your ultimate, and pretty much just spam your abilities and escape from the turret with your W).